The Congregation of the Humility of Mary was founded in France in Napoleonic times. As a small congregation it emigrated to the USA and settled in Pennsylvania (http://www.humilityofmary.org/index.html
) and later some nuns migrated to Iowa (http://www.chmiowa.org/contact.cfm
). The latter web-site looks a likely source for information. There is a contact page that gives postal details and an email form. You should address your query to "Sister Archivist".